A new test for human
papillomavirus (HPV) is just as sensitive as the old one, but more
specific for detecting cervical cancer, meaning that it has fewer false
positive results, according to a paper in the February 2011 Journal of Clinical Microbiology.

“This is important
because reducing false positive results avoids unnecessary additional
tests and follow-up, the associated health care costs, and distress to
women,” says first author Sam Ratnam, of the Faculty of Medicine,
Memorial University, St. John’s, Newfoundland and Labrador. HPV
infection, he explains, is highly prevalent, but “only a small fraction
of the infected are at risk of developing HPV-associated cancers.”

The investigators
report that the new test, called the Aptima HPV test, detected 96.3
percent of women with high-grade cervical intraepithelial neoplasia or
worse (CIN 2+) compared to 94.3 percent for the old test, the Hybrid
Capture 2 DNA test (HC2), among 1418 women studied. But Aptima has far
fewer false positives than HC2. “This difference could be attributed
to the fact that the Aptima test detects the expression of two
oncogenes, E6 and E7, via their messenger RNAs,” says Ratnam. “These
proteins are involved in initiation and mediation of oncogenic process
that leads to cervical cancer, and to other HPV-associated cancers. The
HC2 test, on the other hand, detects the viral DNA which is not as
discriminating. The Pap smear, the traditional common screening method
for cervical cancer, has few false positives, but fails to detect
nearly half of all CIN 2+ cases.”

While HPV is the single
most common sexually transmitted virus, its spread is increasing due to
rising oral sex among young people, according the Oral Cancer
Foundation. “We’re seeing more and more cases of tonsilar cancers in
Newfoundland,” a cancer which is frequently caused by HPV, says
coauthor Adrian Lear of the Dr. H. Bliss Murphy Cancer Centre, St.
John’s, Newfoundland. In people under the age of 50, HPV-associated
oral cancers may even be replacing tobacco as the primary causative
agent according to the Oral Cancer Foundation.

While the role of HPV
is most recognized in cervical cancer, it is also associated with anal
and penile cancers, and cancers of the vagina and vulva. The test could
detect HPV infections that have begun to progress towards these other
HPV-associated cancers, says Ratnam.

Currently, two vaccines
are available against HPV: Gardasil, which is active against four
types, 16, 18, 6 and 11, and Cerverix, which is active against two
types, 16 and 18. Types 16 and 18 account for about 70% cervical cancer
world-wide, and types 6 and 11 account for over 90% of genital warts.
These vaccines are now approved in many countries around the world but
offered only to females. “I’m convinced the day is coming when the
vaccine will be offered for both males and females through publicly
funded programs,” says Lear. “In the meantime, the use of a more
accurate test such as the Aptima test should improve the efficiency and
cost-effectiveness of cervical cancer screening around the world, and
should help prevent cervical cancer,” says Ratnam.